I am trying to generate a map of my small office network. I am looking for a software package that can tell me what type of device is at each ip address (printer, win xp desktop, linux desktop, etc.). Does anybody know of an open source package that can do something like this? Doesn't have to draw pretty pictures or anything. Generating a report for me to read would be great.

NMap ("Network Mapper") is an open source utility for network exploration or security auditing. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) they are offering, what operating system (and OS version) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. Nmap runs on most types of computers, including Linux/BSD/Mac OS X, and Windows. Both console and graphical versions are available.